Arc welding apparatus.



T. VARNEY.

ARC WELDING APPARATUS.

APPLICATION FILED SEPT. 18, 1911.

1,095,300, Patented May 5, 1914.

WITNESSES: INVENTOR 5AM Z BY v ATTORNEY UNITED sTA'rEs PATENT OFFICE. f

THEODORE VARNEY, or PITTSBURGH, PENNSYLVANIA, ASSIGNOR mo WESTING- HOUSEELECTRIC AND MANUFACTURING COMPANY, A CORPORATION or PENN- SYLVANIA.

ARC WELDING APPARATUS.

' specification.

My invention relates to electric welding and particularly to the controlof the circuits for arc welding.

The object of my invention is to provide a simple control system adaptedto automatically govern the current in the welding circuit of arcwelding outfits whereby the welding current may be maintainedsubstantially constant and the operation of the outfit materiallyimproved.

According to my present invention, I provide avariable resistance in thewelding circuit, an electric motor for adjusting the amount ofresistance included in the circuithaving an armature which is connectedin shunt relation to the welding arc and a field magnet winding which isconnected either in series with the welding circuit or in a derivedcircuit therefrom.

T e single figure of the accompanying dra\ ing is a diagrammatic view ofa system of control arranged in accordance with my invention.

Referring to the drawing, energy is supplied from any suitable sourcethrough line conductor 1 and a'variable resistance 2 to an arc weldingelectrode 3, circuit being completed from the work on which the weldingis being done, through a conductor 4, a switch 5 and opposite lineconductor 6.

The variable resistance 2 1s connected at its ends and at variousintermediate points to a plurality of stationary contact members 7 inthe usual manner, which are arranged substantially in the arc of acircle and may i be successively engaged by a movable contact arm 8..The arm 8 is normally held in its off posit-ion against a stop 9 bymeans of a spring 10, in which position all of the re sistance 2 isincluded in the welding circuit.

The movable arm 8 is operatively connected to an armature 11 of a smallcontrol motor which is provided with a field magnet winding 12. Thearmature of the motor is connected in shunt circuit relation to thewelding arc, while the field magnet winding 12 is connected to theterminals of a shunt 13,

v Specification of Letters Patent.

Application filed September 18, 1911. Serial No. 649,917.

Patented May 5, 1914.

which is included in the welding circuit. 8

The motor field magnet winding may be included directly inthe weldinglcircuit and.

the shunt 13 omitted within t scope of my invention.

The operation of the system is as follows: Assuming that the partsoccupy the positions shown in thedrawings, the arm 8 being in its offposition and the switch 5 being opened, if the switch 5 is closed andthe electrode 3 is brought into engagement with the surface to bewelded, a circuit is completed from line conductor 1, through conductor14, arm 8, resistance 2, conductor 15, electrode 3, conductor 4, theshunt 13 and the e spirit and field magnet winding 12, the switch 5 andconductor 16 to line conductor 6. As long as the electrode is inengagement with the surface of the work, the resistance is so low thatpractically no voltage is applied to the motor armature 11. As soon asthe electrode is drawn away from the work an arc is established and itsresistance is sufiicient to impress a material voltage across the motorarmature and produce such a rotation of the arm 8, as to exclude theresistance 2. The greater the resistance of the arc, the higher thespeed of the motor, and. on the other hand, if the electrodeis againbrought into engagement with the work, the voltage will be cut off inthe motor armature and the spring 10 will immediately return the arm 8to its initial position.

From the foregoing, it is evident that the current of the weldingcircuit will be substantially constant.

If the arm 8 is rotated suflicient-ly to exclude the whole of theresistance 2, it will come into engagement with a stop 17 and, while themotor will still produce a torque, its armature will be at rest.

- I do not desire to be limited to the specific arrangement illustratedsince it is evident that variations may be etfected in the circuitconnections and inthe arrangement of parts without departing from thespirit of my invention.

I claim a my invention:

1. A system of arc welding comprising a welding circuit, a variableresistance therefor and a resistance varying motor having an armatureconnected in shunt circuit relation to the welding are.

2. A system of arc welding comprising a welding circuit, a variableresistance therean armature connected in shunt circuitrelation to thewelding arc and a field magnet winding which is energized in response tothe current traversing the welding circuit.

3. A system of arc welding comprising a welding circuit, a variableresistance therefor, a shunt connected to the welding circuit and aresistance varying motor having an armature connected in shunt circuitrelation to the welding arc and a field magnet Winding connected to theterminals ofsaid shunt.

a. A control system comprising an elec? tric arc-producing means, aconstant potenv circuit with the arc and means for varying theresistance to maintain a substantially constant current through the arccircuit, said means comprising a motor having armature and field magnetwindings, one of said windings being responsive to the current in thewelding circuit and the other responsive to the voltage across the arc.

In testimony whereof, I have hereunto subscribed my name this 12th dayof September, 1911.

" I THEODORE VARNEY.

Witnesses:

D. H. MACE, B. B. HINns.

